IN THE biggest test so far of Nigeria's transition to democracy, paramilitary police with orders to shoot rioters on sight rushed to suppress a new outbreak of violence in Lagos yesterday after clashes between Nigeria's biggest ethnic groups killed more than 40 people. The alert was issued in the Ogba district of Nigeria's commercial capital.

In another Lagos suburb, Ketu, more than 16 bodies, most charred after being set ablaze with petrol and many hacked with machetes, lay on the streets following the deaths of at least 27 people on Thursday. Residents said 15 children and their teachers were butchered at a nursery school.

Police feared copycat flare-ups between Hausas and Yorubas - Nigeria's biggest and most influential ethnic groups - elsewhere in the country and asked Nigerian broadcasters to refrain from using pictures of the Lagos clashes.

Separately, as reporters were barred from entering areas of ethnic tension in the Niger Delta, embassies were told to stop issuing automatic visas to foreign journalists. The Lagos security clampdown, ordered by President Olusegun Obasanjo, was centred on Ketu. Local journalists said the official death toll, 27, was probably a vast under-estimate.

Ketu, near Lagos airport, is a flashpoint because it has a large market and traders - whose specialisms are often determined by their tribe - meet there. The area has a considerable Hausa population, the northern tribe which is a minority in Lagos and the rest of the south-west. Nigerian democrats view an ethnic crisis as the biggest threat to President Obasanjo, who has proved himself a reformer since his election in February ended 15 years of military rule.

During their years in power, successive juntas argued that only they could keep Nigeria from splitting along tribal lines. The military remains sufficiently powerful to stoke ethnic frictions if it wishes to destabilise the civilian government.

Nigeria, which is Africa's most populous country and one of the world's top oil producers, has witnessed widespread bloodshed since Mr Obasanjo's inauguration at the end of May. From the time of independence from Britain in 1960 until his election this year, the country had known mainly Hausa- dominated, military rule.

President Obasanjo is a Yoruba. But, when he was elected, he was seen as an acceptable candidate for the Hausas because he is a former general. But despite an economic upturn, the population remains restive. Life for the ordinary Nigerian has not improved. Government institutions, such as the Senate, are widely seen as places where the corrupt military have re-invented themselves as democrats.